By mass-producing elements each in which optical waveguides are formed, it is desired to reduce manufacturing cost thereof. According to PATENT DOCUMENT 1, long and narrow stripe-shaped optical waveguides are cut out by sequentially film-forming a clad layer and an optical material layer on a silicon wafer, and subsequently etching the optical material layer. Then, optical waveguide elements each are separated on the silicon wafer by forming long and narrow grooves by etching, the grooves each reaching the silicon wafer after passing through the optical material layer and the clad layer. Next, the silicon wafer is divided along the foregoing grooves to obtain a number of optical waveguide element chips.
However, a method for forming a number of optical waveguide elements in which optical waveguides are formed, on a silicon wafer has been disclosed in PATENT DOCUMENT 1. But no method for forming a predetermined optical fine pattern in each optical waveguide element has been disclosed therein.
On the other hand, it has been considered that a nanoimprinting method is used as a method for forming diffraction gratings and Bragg gratings possessed by a semiconductor laser device. A method for producing the distributed feedback semiconductor laser using a nanoimprinting method has been disclosed in PATENT DOCUMENT 1. In this method, patterning a semiconductor layer for a diffraction grating of the distributed feedback semiconductor laser is carried out by the nanoimprinting method. Further, preparation of a sub-wavelength structure wide-band wave plate using a nanoimprinting method has been disclosed in each of NON-PATENT DOCUMENT 1 and NON-PATENT DOCUMENT 2. Further, it has been disclosed in NON-PATENT DOCUMENT 3 that a nanoimprint technology is applied to prepare optical devices. A wavelength selective element, a reflection controlling element, a moth-eye structure and so forth are exemplified as such optical devices.